Vertically aligned arrays of carbon nanotubes formed on multilayer substrates

Abstract

Multilayer substrates for the growth and/or support of CNT arrays are provided. These multilayer substrates both promote the growth of dense vertically aligned CNT arrays and provide excellent adhesion between the CNTs and metal surfaces. Carbon nanotube arrays formed using multilayer substrates, which exhibit high thermal conductivity and excellent durability, are also provided. These arrays can be used as thermal interface materials.

I claim: 
     
       1. A multilayer substrate for the growth and/or support of a plurality of carbon nanotubes comprising:
 an inert support; 
 an adhesion layer between about 10 nm and about 150 nm in thickness present on one or more surfaces of the support, wherein the adhesion layer consists essentially of iron; 
 an interface layer between about 5 nm and about 50 nm in thickness present on the adhesion layer, wherein the interface layer consists essentially of aluminum or aluminum oxide; 
 
       and
 a catalytic layer between about 10 nm and about 1 nm in thickness located on the interface layer; 
 wherein the adhesion layer and the catalytic layer have the same chemical composition, thereby reducing migration of the catalytic layer into the interface layer during nanotube synthesis and increasing yield and density of the carbon nanotubes formed on the catalytic layer relative to yield and density of carbon nanotubes formed on a multilayer substrate having a catalytic layer with a different chemical composition that that of an adhesion layer. 
 
     
     
       2. The substrate of  claim 1 , wherein the inert support is a metal selected from the group consisting of aluminum, platinum, gold, nickel, iron, tin, lead, silver, titanium, indium, copper, or combinations thereof. 
     
     
       3. The substrate of  claim 1 , wherein the inert support is a metal alloy. 
     
     
       4. The substrate of  claim 3 , wherein the alloy is copper-tungsten pseudoalloy, diamond in copper-silver alloy matrix, or combinations thereof. 
     
     
       5. The substrate of  claim 1 , wherein the support is selected from the group consisting of silicon carbide in an aluminum matrix, beryllium oxide in beryllium matrix, or combinations thereof. 
     
     
       6. The substrate of  claim 1 , wherein the adhesion layer is between about 10 nm and about 100 nm in thickness. 
     
     
       7. The substrate of  claim 1 , wherein the interface layer is between about 7 nm and about 30 nm in thickness. 
     
     
       8. The substrate of  claim 1 , wherein the catalytic layer is between about 5 nm and about 1 nm in thickness. 
     
     
       9. The substrate of  claim 1 , wherein the adhesion layer is about 30 nm in thickness, the interface layer is about 10 nm in thickness, and the catalytic layer is about 3 nm in thickness. 
     
     
       10. The substrate of  claim 1 , wherein the interface layer has a chemical composition which is different from the chemical composition of the adhesion layer and the catalytic layer. 
     
     
       11. An array of carbon nanotubes formed on the substrate of  claim 1 , wherein
 the interface layer is formed of a plurality of aluminum oxide nanoparticles or aggregates; 
 the catalytic layer is formed of a plurality of catalytic nanoparticles or aggregates deposited on the aluminum oxide nanoparticles or aggregates; and 
 a plurality of vertically aligned carbon nanotubes are attached to the catalytic nanoparticles or aggregates. 
 
     
     
       12. The array of  claim 11 , wherein the nanotubes are present at a density between about 1×10 8  and 1×10 10  nanotubes per mm 2  on the inert support. 
     
     
       13. The array of  claim 11 , wherein the nanotubes are present at a density between about 1×10 9  and 1×10 10  nanotubes per mm 2  on the inert support. 
     
     
       14. The array of  claim 11 , wherein the nanotubes are present at a density between about 1×10 7  and 1×10 11  nanotubes per mm 2  on the inert support. 
     
     
       15. The array of  claim 11 , wherein at least 90% of the carbon nanotubes remain on the surface after sonication in ethanol. 
     
     
       16. The array of  claim 11 , further comprising one or more polymers absorbed to the distal ends of the carbon nanotubes. 
     
     
       17. The array of  claim 11 , further comprising one or more metal nanoparticles absorbed to the distal ends of the carbon nanotubes. 
     
     
       18. The array of  claim 11 , further comprising a flowable or phase change material in the space between carbon nanotubes. 
     
     
       19. The array of  claim 11 , wherein the morphology of the array is modified by evaporating a liquid in which the array was immersed. 
     
     
       20. The array of vertically aligned carbon nanotubes according to  claim 11  prepared by a process comprising:
 (a) annealing a multilayer substrate comprising an inert support, an adhesion layer present on one or more surfaces of the support wherein the adhesion layer consists essentially of iron, an interface layer present on the adhesion layer wherein the interface layer consists essentially of aluminum or aluminum oxide, and a catalytic layer, wherein the interface layer is present between the adhesion layer and the catalytic layer and wherein the adhesion layer and the catalytic layer have the same chemical composition; and 
 (b) heating the multilayer substrate to a temperature of between 550° C. and 660° C.; and 
 (c) introducing a carbon source gas. 
 
     
     
       21. The array of  claim 20 , wherein the interface layer has a chemical composition which is different from the chemical composition of the adhesion layer and the catalytic layer. 
     
     
       22. A method of forming an array of vertically aligned carbon nanotubes of  claim 11  comprising:
 (a) annealing a multilayer substrate comprising an inert support, an adhesion layer present on one or more surfaces of the support wherein the adhesion layer consists essentially of iron, an interface layer present on the adhesion layer wherein the interface layer consists essentially of aluminum or aluminum oxide, and a catalytic layer, wherein the interface layer is present between the adhesion layer and the catalytic layer and wherein the adhesion layer and the catalytic layer have the same chemical composition; and 
 (b) heating the multilayer substrate to a growth temperature of between 550° C. and 660° C.; and 
 (c) introducing a carbon source gas. 
 
     
     
       23. The method of  claim 22 , wherein the interface layer has a chemical composition which is different from the chemical composition of the adhesion layer and the catalytic layer.